Measurements of dissolved methylmercury in natural waters using diffusive gradients in thin film (DGT)

2006 ◽  
Vol 8 (12) ◽  
pp. 1242 ◽  
Author(s):  
Olivier Clarisse ◽  
Holger Hintelmann
Keyword(s):  
Thin Film ◽  
Natural Waters ◽  
Diffusive Gradients

Dynamic DGT speciation analysis and applicability to natural heterogeneous complexes

2009 ◽  
Vol 6 (2) ◽  
pp. 170 ◽  
Author(s):  
Raewyn M. Town ◽  
Parthasarathi Chakraborty ◽  
Herman P. van Leeuwen
Keyword(s):  
Thin Film ◽  
Thermodynamic Stability ◽  
Metal Ion ◽  
Natural Waters ◽  
Speciation Analysis ◽  
Metal Species ◽  
Kinetic Regime ◽  
Ligand Ratio ◽  
Diffusive Gradients ◽  
Kinetic Features

Environmental context. The environmental fate and bioavailability of metal ions in natural waters is determined by their thermodynamic stability and kinetic features, both of which are distributed and depend on the metal ion loading of the system. Diffusive gradients in thin film (DGT) is a dynamic technique for metal speciation analysis that measures a certain portion of these complexes as determined by its operational timescale. Reliable interpretation of data furnished by DGT necessitates characterisation of its features for the particular case of heterogeneous complexes. Abstract. Owing to their inherent heterogeneity, the thermodynamic stability of metal ion complexes with natural ligands is characterised by a distribution, and thus is a function of metal-to-ligand ratio. The kinetic features of such metal complexes are also distributed and can be probed by dynamic speciation techniques. The kinetic regime of the metal complex sample can be manipulated via the metal-to-ligand ratio, and the timescale over which kinetic parameters are actually in effect is defined by the window of the chosen technique. Here we detail the kinetic features of diffusive gradients in thin film (DGT), and show that the range of attainable measurement timescales (τ) is rather limited: variation of the gel layer thickness practically allows only one order of magnitude in τ to be scanned. The more effective use of DGT to probe the distribution of dynamic metal species in heterogeneous systems is via variation of the metal-to-ligand ratio in the sample solution. Compilation of the literature DGT data for natural waters shows that by assuming a Freundlich isotherm relationship, the degree of heterogeneity is reflected in the measured DGT concentration as a function of metal ion loading.

scholarly journals In Situ Measurement of Thallium in Natural Waters by a Technique Based on Diffusive Gradients in Thin Films Containing a δ-MnO2 Gel Layer

2018 ◽  
Vol 91 (2) ◽  
pp. 1344-1352 ◽  
Author(s):  
Hongmei Deng ◽  
Mengting Luo ◽  
Xinyao Shi ◽  
Paul N. Williams ◽  
Kexin Li ◽  
...  
Keyword(s):  
Thin Films ◽  
Natural Waters ◽  
In Situ Measurement ◽  
Gel Layer ◽  
Diffusive Gradients

Contribution of organic arsenic species to total arsenic measurements using ferrihydrite-backed diffusive gradients in thin films (DGT)

2012 ◽  
Vol 9 (1) ◽  
pp. 55 ◽  
Author(s):  
Heléne Österlund ◽  
Mikko Faarinen ◽  
Johan Ingri ◽  
Douglas C. Baxter
Keyword(s):  
Thin Films ◽  
Natural Waters ◽  
Arsenic Speciation ◽  
Inorganic Arsenic ◽  
Speciation Analysis ◽  
Arsenic Species ◽  
Future Studies ◽  
Organic Arsenic ◽  
Arsenic Determination ◽  
Diffusive Gradients

Environmental contextBoth the mobility and toxicity of arsenic in natural waters are related to the aqueous species distribution. Passive sampling using ferrihydrite-backed diffusive gradients in thin films (DGT) devices has in previous studies been characterised to measure labile inorganic arsenic, and the possible contribution of organic species has been disregarded. This study shows that the two most prevalent organic arsenic species might be included in DGT measurements, which should be taken into consideration when evaluating DGT data in future studies. AbstractIn previous publications discussing arsenic determination using ferrihydrite-backed diffusive gradients in thin films (DGT) devices, organic arsenic forms have been disregarded, even though it is known that the two most prevalent in natural waters, dimethylarsinate (DMA) and monomethylarsonate (MMA), may adsorb to ferrihydrite and thereby be included in the measurement. In this work the accumulation of DMA and MMA, as well as inorganic arsenite and arsenate, to ferrihydrite-backed DGT devices was investigated. It could be demonstrated that MMA, and under acidic conditions also DMA, adsorbed to the binding layer and might therefore contribute to the total mass of measured arsenic. Diffusion coefficients were measured for all four species to enable quantification of DGT-labile concentrations of organic and inorganic arsenic. Elution of the analytes from the ferrihydrite binding layer was performed using 1 mL of 1 M NaOH to facilitate arsenic speciation analysis using chromatographic separation. Average recovery rates were between 87 and 108 %. This study shows that the contribution of DMA and MMA to the total accumulated mass must be taken into consideration when evaluating DGT data in future studies.

scholarly journals Progress in understanding the use of diffusive gradients in thin films (DGT) – back to basics

2012 ◽  
Vol 9 (1) ◽  
pp. 1 ◽  
Author(s):  
William Davison ◽  
Hao Zhang
Keyword(s):  
Thin Films ◽  
Natural Waters ◽  
Kinetic Studies ◽  
Simple Equation ◽  
Charge Effects ◽  
The Past ◽  
Soils And Sediments ◽  
Rate Of Reaction ◽  
Simple Equations ◽  
Diffusive Gradients

Environmental contextIt is now nearly 20 years since the introduction of the technique of diffusive gradients in thin films, which can provide information on solute concentrations and dynamics in sediments, soils and water. The interpretation of these measurements in terms of concentrations relies on simple equations and associated assumptions. This review examines how well they have stood the test of time. AbstractDiffusive gradients in thin films (DGT) is now widely used to measure a range of determinands in waters, soils and sediments. In most cases the mass accumulated is interpreted in terms of a labile form of the component being measured using a simple equation that applies to steady-state conditions. During the past decade several publications have revealed phenomena that question some of the assumptions necessary for use of the simple equation. This review systematically examines the available evidence relating to appropriate geometry, possible charge effects, binding of solutes and ligands to the diffusive gel and filter, the rate of reaction with the binding layer, the effects of solution complexation and kinetic limitation, necessary time for deployment and the measurement of nanoparticles. DGT emerges as a robust monitoring tool for labile components in solution. Although there is evidence, for some conditions, of binding of metals and, more moderately, humic substances to the diffusive gel and filter membrane, this is unlikely to affect DGT measurement in natural waters for deployment times exceeding a few days. Detailed speciation and kinetic studies require a more thorough interpretation of the mass accumulated by DGT. A coherent theory has emerged for relatively simple solutions, but systems with complex heterogeneous ligands, as is the case for natural waters, are challenging. The size discrimination of DGT is still poorly known. Systematic measurements with well characterised nanoparticles are required to define the distribution of pore sizes in the gels and to establish the contribution of natural colloids to the DGT measurement.

In situ speciation measurements of trace components in natural waters using thin-film gels

Nature ◽  
1994 ◽  
Vol 367 (6463) ◽  
pp. 546-548 ◽  
Author(s):  
W. Davison ◽  
H. Zhang
Keyword(s):  
Thin Film ◽  
Natural Waters ◽  
Trace Components

Assessment of colloidal copper speciation in the Mekong River Delta using diffusive gradients in thin film techniques

2017 ◽  
Vol 188 ◽  
pp. 109-115 ◽  
Author(s):  
Kahyee Cary Seah ◽  
Ghulam Hussain Qasim ◽  
Yong Seok Hong ◽  
Eunsuk Kim ◽  
Kyung Tae Kim ◽  
...  
Keyword(s):  
Thin Film ◽  
River Delta ◽  
Mekong River ◽  
Mekong River Delta ◽  
Copper Speciation ◽  
Diffusive Gradients
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